BRIEF INCUBATION OF GAMETANGIA-BEARING CAPS IN ANTIBIOTICS ELIMINATES BRANCHING IN PROGENY OF ACETABULARIA ACETABULUM (CHLOROPHYTA)1

Branching of the stalk of Acetabularia acetabulum L. (Silva) was investigated by inbreeding and by a brief treatment of gametangia with a variety of antibiotics. The position of the branch along the stalk varied, implying that branching was not restricted to any one time in development (base is oldest and apex is youngest). The branching phenotype was not inherited in Mendelian fashion. Although three microscopic structures (“bubbles,”“pustules,” and “scars”) occurred on the stalks of cells that had branched, these structures were not statistically correlated with branching in the population (n=699 cells). However, brief treatment of gametangia with a new antibiotic mixture did eliminate all macro- and microscopic structures associated with branching of the stalk in the subsequent generation. We could not fulfill Koch's postulates or provide clear evidence for the pathogenic nature of cell branching. Our brief antibiotic treatment of gametangaa of Acetabularia acetabulum was rapid, had no adverse effects, and virtually eliminated branching (and any potential pathogens) from laboratory cultures in the subsequent generations. Our method allows biochemical and molecular analyses to proceed uncomplicated by the possible presence of other organisms and provides a clean baseline for the future selection of mutations that may induce heritable branching.